1. Field of the Invention
The invention relates to fittings for joining sections of pipe, and more particularly to such fittings for repairing leaks in existing piping or joining an additional pipe line to existing pipe where the existing pipe is relatively inaccessible and cannot be removed and replaced without substantial difficulty.
2. State of the Art Prior to the Invention
Plastic pipes have become widely used in sprinkler systems because of their low cost and ease of installation and repair. Such pipes, commonly referred to as PVC pipes because of their typical polyvinyl chloride composition, may be joined without threading by applying an adhesive such as a solvent cement type to the ends of the pipes and slipping a smooth-bored fitting over the ends of the pipes.
When a break occurs in an underground piping system made from PVC piping, it can be repaired by digging away the dirt over the break and then cutting out a small section of pipe that contains the break. A coupling is then placed on the two opposed ends of the cut pipe. A conventional coupling is a simply rigid, hollow, cylindrical section that has an internal diameter that fits snugly over the external diameter of the pipe. Adhesive is applied to the inside surface of one end of the coupling and around the external surface of one end of the pipe. Sliding the coupling over the end of the pipe is done rapidly and effortlessly. Adhesive is now applied to the internal surface of the second end of the coupling and the end of the second pipe. The end of the second pipe must now be slid into the second end of the coupling and great difficultly is encountered in accomplishing this step. The two ends of the pipe are bent as far as possible away from their center lines so that the gap between the second end of the coupling and the end of the second pipe is increased sufficiently to allow insertion of the end of the second pipe into the second end of the coupling and forcing the pipes back into axial alignment which also forces the end of the second pipe into the second end of the coupling. The dirt along a relatively long section on each side of the pipe where the coupling is being installed must be removed to permit sufficient bending of the pipe in existing underground piping systems. This requires considerable labor in both digging away of the dirt as well as replacement of the dirt once the repair is made.
In those situations where a new pipe line is desired to be added to an existing pipe line, dirt must be removed to expose the area of the existing piping to which the second pipe line is to be connected. The existing pipe is cut and a small section removed so that a fitting in the form of a tee or a wye can be connected in line in the existing pipe. These fittings, the tee and the wye, have two ends very similar to the ends of the coupling which was described above, and the two ends of the fittings must be installed in the existing pipe line in the same manner as described above for installing a coupling in the existing pipe line.
It has been acknowledged in the prior art that it would be desirable to provide a fitting that could be installed in an existing piping system without requiring bending of the two pipes to which the fitting is to be connected. The disclosure of a series of inventions is shown in U.S. Pat. Nos. 3,971,574; 4,103,943; 4,109,944; and 4,429,907 wherein a coupling is formed of two semi-cylindrical members which are arranged to enclose and encapsulate the opposite ends of two pipes that are to be connected for fluid flow through the connected pipes. The two semi-cylindrical members are made of plastic and designed to be adhesively bonded to each other and to the two ends of the pipes by a suitable cement so as to provide a water-tight seal. The use of cement to bond the semi-cylindrical members is a very messy procedure, and becomes even more complicated by the required effort of maintaining the semi-cylindrical members in constant, firm contact with the two ends of the pipe until the cement has set sufficiently to hold the assembly in its proper place. The series of developments disclosed in the above-mentioned U.S. Patents are directed to various means of holding the semi-cylindrical members in their proper positions as the cement sets. The use of a liquid cement is still messy, and it would clearly be desirable to have a system in which a liquid cement is not necessary in forming a liquid-tight seal between the two semi-cylindrical members and the two ends of the pipes.